Such a dental implant component is commonly referred to as a "cylinder" in the art but this term is not used herein when specifically referring to the present invention as it implies a circular cross-section of constant diameter for the component which is not the case with the present invention.
A dental prosthesis is one of the components which make up a dental implant which is a structure which is anchored to the jaw bone (maxilla or mandible) of a patient to replace one or more lost natural teeth. A dental implant comprises a dental prosthesis support structure which is anchored to the jaw bone of a totally or partially edentulous patient to support the dental prosthesis. The dental prosthesis support structure is typically formed by (i) one or more anchoring members (fixtures) implanted in the bone tissue of the maxilla or mandible, the number of fixtures used depending on whether the dental implant is to be for a single-tooth replacement, in which case a single fixture is used, or for a multi-tooth replacement, in which case one or, more usually, a plurality of fixtures will be used, and (ii) a transmucosal member (abutment) for each fixture, each abutment being connected to the coronal end of the associated fixture to bridge the soft tissue layer (gingiva) overlying the fixture site. A structure which presents one or more artificial replacement teeth--the dental prosthesis--is then connected to the coronal end(s) of the abutment(s), e.g. a crown for a single-tooth replacement or a bridge for replacement of a number of lost natural teeth.
To ensure that the dental prosthesis fits in with the prevailing conditions in the patient's oral cavity, for instance natural teeth still left in the maxilla or mandible, the dental prosthesis is fabricated with reference to a full-scale model of the toothless jaw prepared in a manner known per se. Usually incorporated in the model are one or more analogue components, the number corresponding to the number of fixtures in the maxilla or mandible. The or each analogue component has an end which is an analogue of the coronal end(s) presented by the dental prosthesis support structure, e.g. by the abutment(s). The analogue component(s) is incorporated into the model so that the analogue end(s) accurately reproduces the position and orientation that the coronal end(s) of the dental prosthesis support structure has, or will have, in the jaw.
A cylinder having a proximal or apical end which complements the coronal end(s) of the dental prosthesis support structure is then seated on the analogue end of each analogue component. A dental prosthesis which fits in with the prevailing conditions in the patient's oral cavity is then fabricated using the cylinder(s) whereupon the dental prosthesis is transferred to the dental prosthesis support structure for anchorage to the maxilla or mandible.
The manner in which the dental prosthesis is fabricated using the cylinder(s) depends on whether the dental prosthesis is for a single-tooth replacement or for replacing a number of teeth and also on whether the dental prosthesis is to be a permanent prosthesis or a temporary prosthesis for use in the interim period while a permanent prosthesis is fabricated.
Permanent dental prostheses are typically formed by applying a wax pattern on the cylinder(s) when mounted on the analogue component(s) and forming a cast structure on the cylinder(s) having the same profile as the wax pattern by the lost-wax casting process in which the cylinder-wax pattern assembly is surrounded by investment material and then "lost" by heating to leave a mould into which a precious or semi-precious metal such as gold is poured via a sprue passing through the investment material. In this regard, the cylinder(s) can be totally or partially formed of a burn-out material, e.g. a plastic such as polystyrene or Delrin.TM. (Du Pont), in which case the burn-out material is also selectively replaced by the metal. The use of the investment material, however, ensures that surface features provided at the apical end(s) of the cylinder(s), for example faces of a male or female polygon, which enable the cylinder(s) to seat on the coronal end(s) of the dental prosthesis support structure are retained in the cast structure when presented by burn-out material.
For a permanent single-tooth dental prosthesis a porcelain layer is fired onto the inner cast framework which includes, or is based on, a single cylinder to give a natural tooth appearance to the dental prosthesis. The wax pattern may or may not be shaped to give the inner cast framework a tooth-like appearance for the porcelain to be fired onto. If not, the porcelain layer is built-up on the framework to give the dental prosthesis a tooth-like form.
Where a number of natural teeth are to be permanently replaced, the dental prosthesis will typically comprise an inner cast framework which includes, or is based on, a number of cylinders and a range of artificial teeth (denture) mounted on the inner cast framework. In this instance, the wax pattern will typically splint the cylinders on the analogues in the model to form a cast framework which can bridge across the spaced-apart coronal ends of the dental prosthesis support structure and the denture will be mounted on the casting either before or after the casting is mounted on the coronal ends of the dental prosthesis support structure. Alternately, the dental prosthesis may be formed by applying an isolated wax pattern to each cylinder to form individual castings which are then mounted to the coronal ends of the dental prosthesis support structure with the denture then being mounted onto the castings.
For an overview on the formation of permanent dental prostheses see inter alia `Dental Implants: A Guide for the General Practitioner`, Michael Norton, Quintessence Publishing, 1995, Chapters 4 and 5.
The use of temporary dental prostheses is well-known and the circumstances in which a temporary dental prosthesis is needed are documented in U.S. Pat. No. 5,259,759 (Jorneus et al/Nobelpharma AB). In the case of a temporary single-tooth dental prosthesis, the usual procedure is to form an acrylic resin artificial tooth on the cylinder by applying the acrylic resin to the outer surface of the cylinder when mounted on the analogue end of the analogue in the model, shaping the acrylic resin to a natural tooth form and then curing the acrylic resin.
Although it is common for a dental prosthesis or core part of a dental prosthesis fabricated on one or more cylinders to be mounted to a fixture-abutment assembly or series of such assemblies, it is also known for a dental prosthesis or core part of a dental prosthesis fabricated on one or more cylinders to be mounted to a fixture or series of fixtures direct. In this case, the or each cylinder has a proximal end which complements the coronal end of the or each fixture and each analogue component in the model will have an end which is an analogue of the coronal end of the fixture(s).
The aim of the present invention is to provide a dental implant component for a dental prosthesis or core part of a dental prosthesis to be fabricated on which has advantages over the hitherto proposed cylinders in the art.